Your story is very common. Some people say that it is easier to find someone to marry than find a compatible dance partner. Probably a slight exaggeration. But you get the point. You are even lucky that your partner is not maliciously teasing you.

Try this: Tell your partner honestly how you feel and tell her that you want to end the partnership, or at least reduce it to occasional practices, unless you involved romantically, in which case you are stuck, no one can help you. Get a good professional teacher, fitting in height, take lessons and do Pro-Am competition. You will be surprised how your confidence and knowledge increases.